There are image formation devices each of which discharges a discharge liquid by providing a heater to a recording head and heating the discharge liquid in the recording head to a predetermined temperature by electric conduction to the heater so that the discharge liquid has a viscosity which can be discharged.
Though various discharge liquids can be used in such image formation devices, in recent years, the requirement for recording and forming images has been increased even on a recording medium such as a plastic sheet which does not absorb a discharge liquid well. Thus, instead of general dye discharge liquid and pigment discharge liquid, an ink such as a gel ink, hot-melt dry ink and wax ink is used, the ink being in a gel form or solid at an ordinary temperature and changing in phase to a liquid form with a lower viscosity by heating (hereinafter, such discharge liquid is described as a phase transition ink).
Since such discharge liquid becomes mostly gelled or solid at a normal temperature, when landing on the recording medium, the viscosity rapidly increases, and thus, it is possible to prevent the image deterioration due to combined adjacent drops of discharge liquid. Accordingly, there is a merit in that recording can be performed with high image quality without generating color mixture even on the above-mentioned recording medium which does not absorb the discharge liquid well.
In an image formation device, the discharge liquid is generally supplied to the recording head via the outside of the recording head, for example, through a supplying flow channel from a discharge liquid tank storing the discharge liquid separately. Thus, it is necessary to not only maintain the stability of viscosity when discharging the liquid but also maintain a predetermined viscosity on a supplying path from the discharge liquid tank to the recording head in order to supply the discharge liquid stably. Especially, this is remarkably necessary for the above-mentioned phase transition ink which sensitively changes in viscosity due to the temperature.
In such circumstances, there are known techniques to heat the supplying path itself as a configuration for heating the ink supplied from outside of the recording head main body (patent documents 1 and 2).
In the patent document 1, in order to efficiently heat the ink supplied to the recording head, a heater is embedded in a base body forming a flow channel for supplying the ink to the recording head, the ink being supplied from outside the recording head, and the heater heats the discharge liquid flowing through the flow channel.
In the patent document 2, in order to evenly heat the ink flowing through the supplying path, the flow channel connecting the recording head and the discharge liquid tank is wounded around the heater, and the discharge liquid flowing through the flow channel is heated.